It has been awhile since I've been tinkering with the tune of the Charger. Mainly my delay stems from the fact that I have a cam swap planned that would render any current tune ineffective. I'm swapping out the Lunati 316/326 for the Mopar 284/528 to gain better low rpm street manners. The MP cam with less overlap should improve things.
Today a buddy came over with his 71 Challenger. He has the same brand of wideband guage as I, the AEM.
Paul wasn't happy with the performance of the car since he did a cam swap. He had been tinkering with the carburetor and timing to try to improve the A/F #s and the power but the car ran too lean at idle, too fat at WOT, power was down and it dieseled upon shutdown even with a 900 idle. He has a 5 speed from American Powertrain and the engine is a 340 based 416 with a Holley Street Avenger 770.
His timing was set to an initial of 10 and a total or 25. He said that he had it set there because any more timing made the dieseling worse. I learned HERE that ignition timing is often blamed for the "run-on" condition but isn't always the case.
I disconnected the throttle cable and backed off the idle speed screw, then ran the engine at 3000 rpms. After 25-30 seconds, I let the engine rev down, then shut it off. NO run on, no spitting, snorting, just silence. I told him that his dieseling was probably due to partially open throttle blades at idle. I bumped the timing to 18 initial, 33 total and backed out the idle mixture screws to get the guage in the 14-15 zone.(Idle in neutral) The car runs great, makes more power than before and does not run on. It still reads rich at cruise so I think it is in the same situation as I am with the Charger: It needs smaller primary jets with a bigger PVCR.